The present invention relates to a lens grinding apparatus for grinding the periphery of an eyeglass lens so that it conforms to the user's eyeglass frame. The invention also relates to an eyeglass lens layout input device for entering data to be used in providing a layout of each lens that corresponds to the eyeglass frame and which sends said layout data to an apparatus for grinding the lens.
An apparatus is known that is supplied with data on the configuration of the user's eyeglass frame or a template therefor and which grinds the periphery of eyeglass lens so that it conforms to the frame on the basis of the entered configurational data. To provide a layout for the optical center of each lens with respect to the shape of the user's eyeglass frame or a template therefor, the apparatus is supplied with the pupillary distance of the user and various other kinds of layout data. To this end, the apparatus has switches that are depressed to select specific items of layout data and ENTRY switches that are also depressed to enter the desired numeric values of a selected item. A known type of such ENTRY switches consists of a "+" key for increasing the numeral and a "-" key for decreasing it.
The "+" and "-" keys are also used to alter the edge position of a lens with respect to its configuration when displaying an image simulating the bevel shape.
Entering numeric values by means of key switches has had the following problems. In order to make a substantial change in numeric values, either the "+" or "-" key switch is kept depressed until a value near the desired one is reached and, thereafter, the switch is depressed finely enough to increment or decrement the value step by step. The first stage of the entering operation requires a careful watch of the displayed numeral; otherwise, the number you get will deviate greatly from the desired value. If the desired value is exceeded, an extra keying action is required to return to the desired value. If the desired value is yet to be reached, a fine adjustment is necessary. In addition, it takes time to make a substantial change in numerals. Thus, entering numeric values through the manipulation of key switches has not been highly efficient mainly because it is a nerve-racking job to obtain the desired value.
A further problem with the manipulation of key switches is that when altering the sectional edge position of a lens with respect to its configuration while looking at the image simulating the bevel shape, an alteration to the desired position is not a sensible step if it is done by manipulation of key switches.